1. Field of the Invention
The present invention relates to a method of and apparatus for removing contaminants, such as particles and organic material, from a semiconductor substrate or a liquid crystal display (LCD) substrate.
2. Description of the Related Art
In the process of manufacturing an integrated circuit (IC), such as a memory device or an LCD, the surface of a substrate of the IC may be contaminated. Contaminants on the surface of a substrate may include organic material, dust, residue, and metal contaminants. Such contaminants may be divided into two types: organic materials that can be removed mainly by a chemical reaction and particles that can be removed mainly by physical force. This contamination typically occurs when the substrate is being stored or is in a stand-by state between successive processes. The contaminants may create defects that ultimately cause the integrated circuits to malfunction. For example, organic residue on the surface of a substrate may cause a defect in a subsequently formed thin film or may increase the contact resistance of the device.
Thus, a step of cleaning the surface of a substrate, such as a wafer, is attendant to each process performed in the manufacturing of an integrated circuit such as memory device or an LCD. The cleaning is performed to remove organic contaminants or contaminant particles from the surface of the substrate. Conventional wet cleaning techniques have been used for cleaning the surface of a substrate. It is well-known that these wet cleaning techniques are very effective in removing contaminant particles from the surface of a substrate. Furthermore, the wet cleaning techniques include the use of a spin brush during cleaning or an ultrasonic or megasonic cleaner to enhance the cleaning effect.
Despite the significant efforts directed towards cleaning the surface of a substrate, the effectiveness of conventional wet cleaning techniques is quite limited when the circuit patterns of the memory device or LCD are extremely fine. For example, the use of a spin brush or an ultrasonic cleaner may damage the fine patterns of a memory device or an LCD. Furthermore, although a spin brush or an ultrasonic cleaner in a wet cleaning process may be effective in removing large contaminant particles, they are hardly effective in removing particles on the order of submicrons.
Furthermore, along with the miniaturization of the patterns, there is a trend in which a gate or a bit line includes metal such as tungsten (W). Many conventional wet cleaning processes would be detrimental to the metal. Therefore, wet cleaning a substrate on which such a gate or bit line has been formed is limited to rinsing the substrate with deionized water or a minimal cleaning using a stripper. In these cases, it becomes increasingly difficult with any reliable degree to effectively prevent a defect from occurring during a fabrication process.
Recently, a number of new cleaning techniques have been developed for removing contaminants such as particles or organic residue. For example, according to one approach, an aerosol including microscopic frozen particles is sprayed over the surface of a substrate to remove contaminants from the surface of the substrate. U.S. Pat. No. 5,967,156 issued on Oct. 19, 1999 to Peter H. Rose et al., and entitled “Processing A Surface,” describes a such a method.
More specifically, the patent discloses a method of removing foreign material (for example, particulate contaminants such as dust and metals, and organic material such as photoresist and fingerprints, and residue) from the surface of a substrate by reacting a reactant gas with the foreign material. An aerosol including frozen particles is applied along with a flow of the reactant to the surface of the substrate to aid the reaction of the reactant gas with the foreign material. The surface of the substrate is irradiated with infrared (IR) or ultraviolet (UV) light to heat the substrate, and thereby further aid the reaction of the reactant gas with the foreign material.
However, the effectiveness of the aerosol in cleaning the surface of the substrate is reduced because both the physical and chemical cleaning processes are performed simultaneously in the same place. More specifically, the ultraviolet or infrared light produced during the chemical cleaning process may reduce the effectiveness of the aerosol because ultraviolet and infrared light are radiant forms of energy. Therefore, the ultraviolet or infrared light is absorbed by the walls of the processing chamber and at the surface of the substrate, in particular, by contaminants on the substrate surface or by the reactant fluid. Furthermore, the ultraviolet or infrared light may also be absorbed by the nozzle from which the aerosol issues. Therefore, the temperature inside the processing chamber may rise so much as to preclude frozen particles from issuing from the nozzle. Even if the frozen particles do issue from the nozzle, there is high possibility that the frozen particles will evaporate before reaching the surface of the substrate. Thus, there are hardly any frozen particles to collide with contaminant particles.
Accordingly, it is highly desirable to provide a method of and apparatus for effectively removing contaminants, such as organic residues or particles, from the surface of a substrate.